Testing the camshaft position (CMP) sensor B is a pretty easy and straightforward process that can be performed with a standard multimeter. In this tutorial, I'll guide you through the entire testing procedure step by step.
By the end of the tutorial, the three tests outlined here will help you to determine whether the CMP Sensor B is functioning properly or is toast and requires replacement.
And if you'd rather skip the testing and just replace it, that's fine too. I'll point you to a quality sensor from a trusted brand I've been using for years —one I can recommend without hesitation.
Contents of this tutorial:
- Symptoms Of A Bad CMP Sensor B (Exhaust Cam – Cylinder ID).
- Should I Just Replace The CMP Sensor Without Testing It?
- Where To Buy The CKP Sensor And Save.
- How the CMP Sensor B Works.
- TEST 1: Checking The CMP Signal With A Multimeter.
- TEST 2: Making Sure The CMP Sensor Is Getting 12 Volts.
- TEST 3: Making Sure The CMP Sensor Is Getting Ground.
- More 2.4L Honda Accord Tutorials.
APPLIES TO: This tutorial applies to the following vehicles:
- 2.4L Honda Accord: 2003, 2004, 2005, 2006, 2007.
CMP SENSOR WIRING DIAGRAM:
CMP SENSOR A DIAGNOSTIC TESTS:
CKP SENSOR DIAGNOSTIC TESTS:
Symptoms Of A Bad CMP Sensor B (Exhaust Cam – Cylinder ID)
The 2003–2007 2.4L Honda Accord comes equipped with two camshaft position sensors:
- Sensor A (intake side): Used by the PCM to monitor and control the VTC (Variable Timing Control) system.
- Sensor B (exhaust side): Used as the cylinder identification signal so the PCM knows exactly where cylinder #1 is in the cycle.
On these Accords, CMP Sensor B is the PCM's "home" signal, telling it where cylinder #1 is. By combining the CMP Sensor B signal with the CKP sensor signal, the PCM can time fuel and spark correctly to start and keep the engine running.
When CMP Sensor B goes begins to fail or dies, you'll feel it. Here's what usually shows up:
- Extended crank or no-start: The engine spins and spins because the PCM loses the cylinder ID cue it needs to sync injection and ignition.
- Starts, then stalls: The engine may catch for a second (right after key-on prime), then shut off as soon as the PCM realizes it can't stay in sync.
- Random misfire at idle: An intermittent CMP B signal can throw off phasing at low RPM, which shows up as a shaky idle that comes and goes.
- Rough cold start, smoother when warm: Thermal expansion can "heal" a borderline sensor or connector (for a while), which is why the problem feels worse first thing in the morning.
- Loss of power on tip-in: Hesitation or a flat spot when you crack the throttle, since the PCM may drop out of proper sequential control when the sync signal cuts out.
- Bad gas mileage: When phasing isn't reliable, fuel delivery and spark timing aren't as precise, which wastes fuel in everyday driving.
- Intermittent stall at stops: Rolling to a light, RPM dips and the engine may die; restarts after a key cycle are common if the fault is intermittent.
- Illuminated Check Engine Light with CMP B codes: You'll typically see one of these:
- P0365: CMP Sensor B No Signal.
- P0369: CMP Sensor B intermittent Interruption.
ENGINE NO-START DIAGNOSTICS: If you're diagnosing an engine no-start problem, this guide is a good resource:
Should I Just Replace The CMP Sensor Without Testing It?
Most folks, when troubleshooting a CMP Sensor B issue, will simply remove the old one and install a new one without actually testing it first. This usually makes a lot of sense when you're seeing something like this:
- The check engine light is on with a CMP Sensor B diagnostic trouble code.
- The engine won't start, or it's stalling off and on.
- And there are no other codes stored.
Truth be told, in most cases, that's exactly what solves the problem. And the three biggest reasons this diagnostic strategy works are:
- The CMP sensor is an inexpensive ignition system component: Replacing it to see if it fixes the problem is a pretty low-risk diagnostic move.
- It's not that hard to replace: With the right tools and a little patience, you can swap it out in under 30 minutes.
- Testing it can be tricky: On paper, testing the CMP sensor looks easy. In the real world, it can be challenging for some folks.
So for a lot of people, even if replacing the sensor doesn't solve the issue, the cost is just part of the diagnostic process. If swapping it out with a new one fixes the problem —great, life goes on. If it doesn't, well, now it's time to dig a little deeper.
There's nothing wrong with that approach. If that's the route you're taking, here are two CMP sensors I recommend from brands I've used and trusted for years —and still do.
- Hitachi CPS0221 Engine Crankshaft Position Sensor (Amazon affiliate link)
- Delphi SS10931 New Crankshaft Sensor (Amazon affiliate link).
But if you're like me and you want to know for sure the CMP sensor is bad before replacing it, then in this tutorial I'll walk you through the process (which isn't difficult at all).
Where To Buy The CKP Sensor And Save
When it's time to put in a new CMP sensor, I'm particular about the parts that go into the vehicles I work on. I stick with brands that have proven themselves out in the real world and this means no knockoffs. Below are two solid options you can get on Amazon —brands I've used over and over, and still trust to get the job done right.
Disclosure: As an Amazon Associate, I earn from qualifying purchases. Buying through these links helps support this site at no extra cost to you. Thanks for your support —it really means a lot!
How The CMP Sensor B Works
The camshaft position (CMP) sensor B is mounted on the exhaust camshaft side (firewall side) of the cylinder head. Like CMP Sensor A, it's a Hall-effect sensor, but its trigger wheel design is different and serves a different purpose.
To successfully test the sensor, here's what you need to know about how it works:
- The exhaust camshaft's trigger wheel has five teeth total —four are spaced evenly around the wheel, and one is positioned very close to another. That closely spaced pair is the PCM's "home" or cylinder identification signal.
- The CMP sensor B has 3 wires in its connector:
- It receives 10–12 Volts from the yellow with black stripe (YEL/BLK) wire when the key is in the ON or START position.
- It has a constant chassis Ground from the brown with yellow stripe (BRN/YEL) wire.
- The signal it generates is sent to the PCM through the green (GRN) wire.
- As the engine is cranked or running, each tooth passing under the sensor switches the signal voltage from high (~5 Volts) to low (near 0 Volts), producing an ON/OFF pulse.
- There will be a total of five ON/OFF pulses for every two crankshaft revolutions (one full camshaft rotation).
- The PCM uses the evenly spaced pulses for general cam position tracking, and the short-gap pair to pinpoint cylinder #1's position in the firing order.
For your CMP Sensor B testing purposes, it's important to remember that because the camshaft spins at half the crankshaft speed, you'll need to rotate the crankshaft pulley two complete turns to see the full pulse pattern.
Turning it only one crankshaft revolution will give you about two or three pulses, depending on where you start, and you may miss the unique short-gap pair without completing the full two-turn cycle.
TEST 1: Checking The CMP Signal With A Multimeter
The first step in diagnosing a bad CMP sensor is to see if it's sending out an ON/OFF voltage signal while you rotate the engine by hand.
That signal toggles between ON and OFF. In other words:
- ON: Multimeter reads about 5 Volts DC.
- OFF: Multimeter drops to 0 Volts (anything around 0.2 V counts as zero).
It's important to point out that you'll only get a reliable reading if you turn the engine over by hand —meaning a 1/2-inch ratchet and the correct socket on the crankshaft pulley to rotate it yourself.
If you're in need of a good multimeter, or thinking of upgrading, here's the exact one I use and recommend:
- Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link).
LOCATION: You'll find CMP Sensor B at the back of the cylinder head, on the exhaust camshaft side (firewall side of the engine). To get to it, you'll need to move the air cleaner assembly and the EVAP purge valve out of the way.
IMPORTANT: Before running this test, unplug every ignition coil from its wiring connector. This is a safety precaution that'll prevent the engine from starting during the test.
CAUTION: You'll need to raise the front of the vehicle to access the crankshaft pulley bolt (to manually turn the engine over). Never trust the jack alone —always support the vehicle with jack stands.
NOTE: The CMP sensor has to stay plugged into its 3-wire connector for this test. The easiest way to get to the signal inside wire is by using a wire-piercing probe on the CMP signal wire. If you don't already own one, here's the exact tool I recommend: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).
Follow these steps to perform the test:
- 1
Lift the vehicle and secure it on jack stands (for access to the CMP sensor).
Once the car is safely supported, remove the driver's side splash shield from the wheel well. - 2
Disable the ignition by unplugging each ignition coil from its connector.
This step ensures the engine cannot accidentally start while you're running the CMP sensor check. - 3
Attach the red multimeter lead to the green (GRN) wire at the sensor connector.
The GRN wire carries the signal from the camshaft position sensor to the PCM in your Accord.
NOTE: Keep the CMP sensor plugged into its 3-wire connector during the signal test. Use a wire-piercing probe (or a back-probe method) to connect the red lead to the BLU wire without unplugging the sensor. - 4
Set your multimeter to Volts DC mode.
- 5
Connect the black test lead to the negative (-) battery terminal. I often use a jumper cable to make this connection easy and secure.
- 6
Turn the ignition key to the ON position (Position II) but do not crank the engine.
This powers up the CMP sensor so you can observe its output while turning the engine manually. - 7
Using a 1/2-inch ratchet and the correct socket, rotate the crankshaft pulley clockwise by hand for two complete turns.
NOTE: Use a bright-colored marker to put a reference mark on the crankshaft pulley. This will make it easy to keep track of the revolutions as you turn it.
IMPORTANT: Accuracy depends on turning the engine by hand. Using the starter motor will not give you correct test results. - 8
Watch for an ON/OFF voltage signal on the multimeter (if the sensor is functioning properly).
"ON" means the multimeter shows about 5 Volts DC, and "OFF" means it drops to 0 Volts (anything near 0.2 V counts as zero).
NOTE: You should see a total of five ON/OFF pulses during two full turns of the crankshaft pulley.
Here's how to interpret the results:
CASE 1: The multimeter displayed a clear ON/OFF 5-volt pattern while you turned the engine by hand. This confirms the CMP sensor is producing a proper signal. At this stage, no further testing is needed —if it's outputting a signal, it's already receiving both power and Ground.
CASE 2: No ON/OFF 5-volt signal appeared while turning the engine manually. This often points to a failed CMP sensor. However, you should still confirm that the sensor is getting both power and Ground before replacing it.
Verifying the power and Ground circuits ensures you're not replacing a good sensor when the real issue is elsewhere. Let's start with checking for power: TEST 2: Making Sure The CMP Sensor Is Getting 12 Volts.
TEST 2: Making Sure The CMP Sensor Is Getting 12 Volts
In TEST 1, the results told us the CMP sensor isn't producing the ON/OFF signal the PCM needs to fire up the engine.
The next logical step is to confirm that the CMP sensor is actually getting power. On this system, that means battery voltage —between 10 and 12 Volts DC— with the key in the ON or START position.
The voltage feed to the CMP sensor comes in on the yellow with black stripe (YEL/BLK) wire at the sensor's 3-wire connector.
Here's how to check for power in that circuit with a simple multimeter test:
- 1
Unplug the CMP sensor from its connector.
- 2
Set your multimeter to Volts DC mode.
- 3
Connect the black multimeter lead to the negative (-) battery post.
- 4
Have a helper turn the ignition to ON —but do not start the engine.
- 5
Touch the red multimeter lead to the terminal for the YEL/BLK wire, probing from the front of the connector.
- 6
Your multimeter should show between 10 and 12 Volts DC.
Here's how to read your results:
CASE 1: You see battery voltage on the YEL/BLK wire. That's exactly what we want —it confirms the CMP sensor is receiving the power it needs. The next check is to verify the sensor's Ground: TEST 3: Making Sure The CMP Sensor Is Getting Ground.
CASE 2: No battery voltage on the YEL/BLK wire. This confirms that CMP sensor B isn't getting power and without it, it can function.
Your next step is to troubleshoot and fix the cause of the missing ignition voltage. Doing so will restore the sensor's operation and clear the trouble code from your Accord's PCM.
For help tracing the circuit and pinpointing the problem, use the following wiring diagram:
TEST 3: Making Sure The CMP Sensor Is Getting Ground
At this stage of your CMP sensor diagnostic, your previous tests have confirmed two key things:
- The CMP sensor is not producing an ON/OFF signal (from TEST 1).
- The CMP sensor is receiving battery voltage on the YEL/BLK wire (from TEST 2).
The final step is to verify that the brown with yellow stripe (BRN/YEL) wire is providing a solid chassis Ground.
This Ground is constant —it should always be available to the CMP sensor. To confirm it's present, we'll perform a voltage test similar to the one used in TEST 2 for checking ignition power.
Here's the procedure:
- 1
Unplug the CMP sensor from its connector.
- 2
Set your multimeter to Volts DC.
- 3
Attach the red multimeter lead to the positive (+) battery terminal.
- 4
Have a helper turn the ignition switch to the ON position without starting the engine.
- 5
Using the black multimeter lead, probe the terminal for the BRN/YEL wire from the front of the connector.
- 6
Your multimeter should show between 10 and 12 Volts DC.
Here's how to interpret your test result:
CASE 1: The BRN/YEL wire shows a solid Ground. This is exactly what we're looking for.
If you have confirmed:
- No signal from the CMP sensor (TEST 1),
- The YEL/BLK wire is supplying power (TEST 2),
- And now, a good Ground on the BRN/YEL wire (TEST 3),
…then you can confidently say the CMP sensor has failed and should be replaced.
Here are two CMP sensors I recommend —both from trusted automotive brands I've used many times in the field:
- Walker Products 235-1269 CMP Sensor (Amazon affiliate link).
- Standard Motor Products PC610 CMP Sensor (Amazon affiliate link).
CASE 2: No Ground on the BRN/YEL wire. This rules out the CMP sensor as the source of the problem —without Ground, it can't work at all.
While tracking down the missing Ground is beyond the scope of this guide, fixing that issue will restore CMP sensor function and clear the related trouble code in your Accord's PCM.
For help tracing the circuit and pinpointing the problem, use the following wiring diagram:
More 2.4L Honda Accord Tutorials
You can find a complete list of tutorials for your 2.4L Honda Accord equipped car here:
Here's a small sample of the tutorials you'll find in the index:
- How To Test The TPS With A Multimeter (2003-2006 2.4L Honda Accord).
- How To Test The Fuel Injectors (2003-2007 2.4L Honda Accord).
- How To Test The Ignition Coils (2003-2006 2.4L Honda Accord).
- How To Test The MAP Sensor (2003-2007 2.4L Honda Accord).
If this info saved the day, buy me a beer!
